Motors, such as miniature stepper motors, are widely used, for instance in the automotive industry. Today the automotive industry wants state-of-the-art products, and they also want to be more cost efficient. In an automotive instrument cluster, the pointers of each instrument must be adequately illuminated. The pointers can rotate in both directions in speedometers, revolution counters, fuel indicators, temperature indicators, etc. Each pointer, situated over a graduated dial, will indicate the current value, m which during daytime will be perfectly visible to the driver. During nighttime, the pointers have to be illuminated.
Large pointers usually require three light-emitting diodes (LEDs) each to illuminate the pointer over its 300 degree turning radius. The pointers are generally operated by stepper motors which have a pointer shaft for rotating the pointer. Alternatively the motors are shaftless, in which case the pointer has a shaft that can be connected to the motor. Stepper motors (or step motors) are brushless, synchronous electric motors that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism, as long as the motor is carefully sized to the application.
New generation motors, either shaftless or with a transparent shaft, guide the light of a single printed circuit board (PCB) mounted LED through the centre of the plastic shaft. As the light source is in the centre of the rotating pointer, the light distribution during the rotation stays constant. Thus, a shiftless solution or a transparent shaft motor offers constant illumination over the entire range of rotation, and it also saves the, cost of two LEDs. This concept works only if the motor is mounted on the front side of the PCB, and therefore the single PCB mounted LED illuminates the pointer shaft up through the bottom of the motor. Therefore, to ensure a homogeneous illumination of the pointer over its entire range of travel, a transparent shaft is preferred using only one centred LED. The whole cluster dial can be illuminated by several LEDs situated at various PCB locations. All of the illumination is designed so that the drivers view and interpretation of the instruments is as clear as possible.
However, due to space restrictions and new cluster technologies, there is a need to mount the motors on the rear side of the PCB. However, in doing so, there is no longer mechanical support or electrical power for the LED. This means that generally the pointer can no longer be illuminated through the shaft which results in an inhomogeneous illumination of the pointer.
It is the aim of the present invention to overcome the problems related to mounting the motors on the rear side of the PCB.